The present invention relates generally to steam turbine technology and, more specifically, to the manner in which steam turbine low-pressure inner casings are supported relative to the turbine machine foundation.
Conventionally, the low-pressure (LP) inner casing of a steam turbine is supported on an LP exhaust hood/outer shell structure that is, in turn, supported on the machine foundation. In some prior designs, support arms extending from the inner casing, are located vertically in substantial alignment with the longitudinal centerline of the turbine rotor assembly, coinciding with the axially-extending interfaces between both upper and lower sections of the inner LP casing, and upper and lower sections of the outer exhaust hood structure. In addition, the actual points of support are located away from the foundation proper, and inside the outer shell. See for example, U.S. Pat. Nos. 4,413,948; 3,881,843; and 3,594,095. By supporting the inner casing on the exhaust hood, away from the foundation, the inner casing is susceptible to undesirable deflections resulting from differential thermal growth in the support components due to the high temperatures inside the exhaust hood, as well as internal vacuum conditions caused by the exhaust gases exiting the hood.